Polymeric sheets and articles wrapped therewith

ABSTRACT

A polymeric sheet having low density and comprising a low to non-existent amount of cyclic olefinic polymers (COP) and/or cyclic olefinic copolymers (COC). The overall density of the sheet may be lower than water. The sheet may be stretched and then heat shrinked onto an article. The sheet may be used as a label or package to wrap articles therewith.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application No.11/989,783, which is a national phase filing under 35 U.S.C. 371 ofInternational Application No. PCT/IL2006/000893 filed on Aug. 3, 2006,which claims the benefit of U.S. Provisional Application No. 60/705,195filed on Aug. 4, 2005 and German Application No. 202006001454.3 filed onJan. 31, 2006. The contents of the preceding stated documents areincorporated by reference as if fully set forth herein.

FIELD OF THE INVENTION

This invention relates to polymeric sheets, for example such sheetscomprising cyclic olefinic polymers (COP) and/or cyclic olefiniccopolymers (COC). The relation also relates to articles wrapped withsuch polymeric sheets.

BACKGROUND OF THE INVENTION

In recent years, some novel substances have become commerciallyavailable under the generic titles of cyclic olefinic polymers (COP) andcyclic olefinic copolymers (COC). These substances are known for avariety of uses, such as manufacture of optical lenses, packaging ofpharmaceuticals, packaging for candies, and others.

Another known use of such polymers, is in manufacturing ofbidirectionally oriented polymeric sheets and unidirectionally orientedpolymeric sheets, in which the orientation is in the transversedirection (TD). The latter sheets are useful as sleeves forunidirectionally shrinkable packaging of bottles.

Films that were shrinked in the transverse direction and contained atleast 60% COC and/or COP were reported to closely follow a bottle'sshape without creasing.

SUMMARY OF THE INVENTION

It has been surprisingly found by the inventors, that the properties ofclosely following bottle's shape without creasing, may be achieved withpolymeric sheets comprising COC and/or COP (hereinafter COC/COP) evenwhen they include less than 50% COC/COP, if these sheets are stretchedmonoaxially, preferably in the machine direction.

In the present application and claims the term “monoaxial shrinkage”means shrinkage along one direction or axis of a sheet, for example themachine direction, whilst the direction or axis essentiallyperpendicular thereto, in this case the transverse direction, retainsthe sheet's original dimension, or else changes by no more than 5%-10%.

Thus, according to a first aspect thereof, the present inventionprovides a polymeric sheet stretched along the machine direction, andcomprising 50% or less, preferably 40% or less, most preferably about30% of COC/COP.

In the present description and claims, unless otherwise is indicated,percentages represent the weight of the COC/COP out of the weight of theentire sheet or film.

The invention also provides articles wrapped in polymeric sheets asdescribed above in a wrap-around method, sleeving and twist-wrap method.Sheets for use in wrap-around or sleeving applications preferably havethickness of from about 40 to about 50 μm, whereas sheets used in twistwrap method according to the invention have preferably thickness of fromabout 20 to about 30 μm.

The sheet of the invention, whether being suitable for wrap-around, forsleeving, for twist wrapping, or for any other purpose may be made of ablend comprising COC/COP and other polymeric substances, such as mLLDPE(metallocene linear low density polyethylene), LLDPE (linear low densitypolyethylene), Copo PP (copolymer polypropylene), polystyrenes like PS(polystyrene) and SBC (styrene-butadiene copolymers), polyesters likePET (poly (ethylene terephthalate)) and PETg (Poly (ethyleneterephthalate) glycol), and polymers of non-cyclic olefins, such aspolyethylene, polypropylene, and ethylene propylene copolymer.

The polymeric sheet as defined above may be made of one layer of apolymer comprising COC/COP and other polymeric substances, it may be amultilayer comprising at least one layer of COC/COP and at least onelayer of other polymeric substances, or it may be a multilayercomprising at least one layer made of a blend of COC/COP and otherpolymeric substances.

The various layers may be attached to one another in any means known inthe art per se, for instance, they may be co-extruded together with orwithout adhesive layers between them, they may be laminated by heat orglue, etc.

Non-limiting examples for non-COC/COP polymeric substances useful in theproductions of polymeric sheets according to the invention arepolyolefins, such as polyethylene and polypropylene; polystyrenes suchas PS and SBC; and polyesters, such as PET or PETg.

Preferably, the shrinkage stage of the wrap around process in carriedout in a steam tunnel.

A further advantage of using sheets comprising COC/COP as defined abovein wrap-around labeling may be that the label follows bottle's shapewithout creasing, and offers excellent transparency of as low as 3.0%HAZE (ASTM D 1003) and all this is combined with relatively low price(thanks to the low COC/COP content) and with the high labeling speedprovided by the wrap-around method.

Accordingly, a second aspect of the invention is an article envelopedwith a polymeric sheet according to the invention, wherein the label washeat shrinked onto the article, preferably with steam. Furthermore, thearticle may be enveloped using the wrap-around method, sleeving methodor any other applicable method known in the art.

Another use of sheets according to the invention is for packagingarticles with a twisted polymeric sheet. Twisted packages are in commonuse in candies packaging. Accordingly, the present invention alsoprovides an article, preferably a candy, twist-wrapped in a sheetaccording to the invention. Thus, according to a further aspect of theinvention there is provided an article twist-wrapped with a stretchedpolymeric film as defined above. The film may be stretched in themachine direction, in the traverse direction, or in both directions.Articles wrapped with films stretched at least in the machine directionare preferred, and most preferred are such articles stretched in theshort gap stretching method. The films used for twist wrappingpreferably may comprise at most 50% COC, more preferably at most 40%COC, and most preferably, about 30% COC.

Thus, one embodiment of the invention is a method for wrapping anarticle, preferably a candy; the method comprising wrapping around saidarticle a polymeric film and twisting said polymeric film in thevicinity of the edges of said article, characterized in that said filmis a stretched polymeric film comprising COC/COP.

The polymeric sheet in accordance with the first aspect of the inventionmay have low density (ρ_(p)), i.e. less than the density of water(ρ_(w)), enabling the material from which the sheet is made to floatwhen submerged in water, which is particularly useful in the separationof materials phase of a recycling process which utilizes watersubmersion for articles to be recycled.

Since the density of water is known to be about one gram per centimetercubed (1 g/cm³), and the density of COC/COP is greater than that, thecontent of COC/COP in the sheet, being less than 50% allows the sheet tohave a density lower than that of the water, which is not the case withknown shrinkable polymeric sheets comprising COC/COP, used in packaging.

Thus, in accordance with a third aspect of the invention there isprovided a polymeric sheet adapted to undergo shrinkage in a monoaxialdirection to 85% of it's original dimension or less (15% shrink or more)upon heating of the sheet to 100° C. or less and having a density lessthan the density of water.

In accordance with a fourth aspect of the invention there is provided apolymeric sheet may be adapted to undergo shrinkage in a monoaxialdirection to 60% of it's original dimension or less (40% shrink or more)at temperatures that may be greater than 100° C. and having a densityless than the density of water.

Both the third and fourth aspects of the invention may be constitutedcompletely of materials other than COC/COP.

A sheet according to the third and fourth aspects of the invention maycomprise of more than one material, in which case not all the materialsnecessarily need to have a density less than that of water as long asthe total density of the sheet is less the density of water. Inparticular, at least one of the materials included in the sheet may havea density greater than the density of water. The material in the sheethaving a density greater than the density of water may be, for example,polystyrene (PS) or PETg (Poly (ethylene terephthalate) glycol).

The invention also provides articles wrapped in polymeric sheets inaccordance with the current aspect of the invention, in a wrap-aroundmethod and sleeving method.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In order to better understand the invention and to see how it may becarried out in practice, some exemplary embodiments will now bedescribed.

Example 1

A multi-layer polymeric film, 50 micrometers in thickness, was producedby a blown film process from two polyolefin resins. One of the resinswas mLLDPE (metallocene linear low density polyethylene) produced byExxonMobil and sold under the trade-name of EXCEED™ 1018CA, the densityof which being 0.918 g/cm³, and the other resin was COC produced byTicona and sold under the trade-name of Topas®, the density of whichbeing 1.02 g/cm³. The multi-layer film was processed in ashort-gap-stretching machine produced by Lenzing Aktiengesellschaft,described in U.S. Pat. No. 5,184,379, at a heating temperature of 90°C.-120° C. and a stretch ratio of 1:3 to produce a monoaxially heatshrinkable film.

This film was found to undergo shrinkage, in the monoaxial direction, to20% of it's original dimension (80% shrink), upon heating to 100° C.,and to 40% of it's original dimension (60% shrink) upon subsequentheating to 110° C.-120° C. and offered excellent transparency of as lowas 3.0% HAZE (ASTM D 1003). The density of the film after shrinkage wasabout 0.96 g/cm³.

The obtained film was used for wrapping a polyethylene bottle having afeminine figure shape with a maximal outer diameter of 6.84 cm andminimal outer diameter of 6.05 cm. The wrapping was carried out on aKRONES roll-fed shrink labeling systems type Krones Contiroll 745-C96,with a steam tunnel at temperature of 100° C., at 20,000 bottles perhour.

The wrapping was carried out as follows: the film was wrapped around adrum, cut to form a label, and glue was applied to the label's edges.Then the label was wrapped around the bottle such that one glued edgeattached the label to the bottle and the edges were glued to each other.The label was heated as to shrink onto the bottle.

Example 2

A multi-layer polymeric film was prepared as in example 1, and was usedfor wrapping a mock-up bottle having a feminine figure shape with amaximal outer diameter of 6.84 cm and minimal outer diameter of 5.00 cm.The wrapping was carried out on a KRONES roll-fed shrink labelingsystems type Krones Contiroll 745-C96, with a hot air tunnel attemperature of about 120° C., at 20,000 bottles per hour.

The wrapping was carried out as follows: the film was wrapped around adrum, cut to form a label, and glue was applied to the label's edges.Then the label was wrapped around the bottle such that one glued edgeattached the label to the bottle and the edges were glued to each other.The label was heated as to shrink onto the bottle.

Example 3

A multi-layer polymeric film, 50 micrometers in thickness, was producedby a blown film process from different resins. A inner layer wasproduced of the same mLLDPE (metallocene linear low densitypolyethylene) described in Example 1. The inner layer of mLLDPE wasdisposed between two outer layers of identical composition. The outerlayers were produced from the following blend of polystyrene resins: (i)General Purpose Polystyrene (GPPS) produced by The Dow Chemical Companyand sold under the trade-name of STYRON_(—)678E™ the density of whichbeing 1.05 g/cm³, and (ii) Styrene-butadiene Copolymer (SBC) produced byChevron Phillips Chemical Company and sold under the trade-name ofK-RESIN®, the density of which being 1.01 g/cm³, and (iii) High ImpactPolystyrene (HIPS) produced by Chevron Phillips Chemical Company andsold under the trade-name of VALTRA MA8000 the density of which being1.05 g/cm³. The multi-layer film was processed in a short-gap-stretchingmachine produced by Lenzing Aktiengesellschaft, described in U.S Pat.No. 5,184,379, at a heating temperature of 90° C.-120° C. and a stretchratio of 1:4 to produce a monoaxially heat shrinkable film.

This film was found to undergo shrinkage in the monoaxial direction, to85% of its original dimension (15% shrink) upon heating to 100° C., andto 40% of its original dimension (60% shrink) upon subsequent heating to130° C.-140° C. The density of the film after shrinkage was about 0.97g/cm³.

The obtained film was used for wrapping a PET (polyethyleneterephthalate) bottle having a feminine figure shape with a maximalouter diameter of 6.75 cm and minimal outer diameter of 5.94 cm. Thewrapping was carried out on a KRONES roll-fed shrink labeling systemstype Krones Contiroll 745-C96, with a hot air tunnel at temperature ofabout 120° C., at 20,000 bottles per hour.

The wrapping was carried out as follows: the film was wrapped around adrum, cut to form a label, and glue was applied to the label's edges.Then the label was wrapped around the bottle such that one glued edgeattached the label to the bottle and the edges were glued to each other.The label was heated as to shrink onto the bottle.

In the current example the density of the multi-layer polymeric filmfrom which the label is made is about 0.97 g/cm³ and the density of thePET material from which the bottle is about 1.3 g/cm³, therefore, thematerial that the label is capable of floating when submerged in waterand the bottle is inclined to sink in water. Consequently the differentcomponents of the article may be separated in a recycling process whichutilizes water submersion for such a purpose.

Example 4

A film was prepared as in example 1, but had a thickness of 25micrometers. The transparency was excellent, as in the film of example1.

The film was found to have the advantage of low back-twist, namely,after it is twisted, it has low tendency to release the twist. It wasfound that when a polymeric sheet according to the invention is twistedin 540 degrees (namely, one and a half full turns), the final twistachieved is of 375 degrees, which is slightly more than a full turn. Asimilar sheet but without the COC/COP provided final twist of 325degrees, which is less than one turn. A similar sheet with the COC/COPbut not stretched provided a final turn of 280°.

The film was successfully used for wrapping lollypops on an Aquarius™machine.

Those skilled in the art to which this invention pertains will readilyappreciate that numerous changes, variations and modifications can bemade without departing from the scope of the invention mutatis mutandis.

1. A method for labeling an article with a polymeric sheet comprising:wrapping the polymeric sheet around the circumference of the article toobtain a labeled article; and heating the labeled article to 100° C. orless, to allow the polymeric sheet to shrink by at least 20% of itsoriginal dimension along a machine direction thereof, to thereby followthe contours of the article, the polymeric sheet having a density lessthan 1 g/cm.
 2. The method of claim 1, wherein the article comprises atleast two portions with cross-sectional diameters that differ from oneanother by more than 20%, being circumferentially enveloped by thepolymeric sheet.
 3. The method of claim 1, wherein the heating iscarried out by steam.
 4. The method of claim 1, wherein the polymericsheet is prepared by short-gap stretching.
 5. The method of claim 1,wherein the polymeric sheet comprises at least two materials, wherein atleast one of the at least two materials has a density greater than 1g/cm.
 6. The method of claim 5, wherein the polymeric sheet comprises upto 50 wt. % of cyclic olefinic copolymer and/or cyclic olefinic polymer(COC/COP).
 7. The method of claim 6, wherein the polymeric sheetcomprises at least one material is polystyrene (PS) or PETg (Poly(ethylene terephthalate) glycol).
 8. The method of claim 1, wherein thepolymeric sheet has a thickness of up to 50 μm.
 9. The method of claim1, wherein the polymeric sheet is shrinkable along an axis perpendicularto the machine direction by no more than 5%.
 10. The method of claim 1,wherein the polymeric sheet is transparent.
 11. The method of claim 1,wherein the polymeric sheet has a density less than 1 g/cm³ aftershrinking.
 12. A method for labeling an article having at least twoportions with cross-sectional diameters that differ from one another bymore than 20%, the method comprising: (a) preparing a polymeric sheet,the polymeric sheet: being monoaxially stretched along the machinedirection, being heat shrinkable along the machine direction by at least20% of its original dimension, being transparent after shrinking, andhaving, prior to and after shrinking, a density of less than 1 g/cm³;(b) wrapping the polymeric sheet onto an outer surface of the article toobtain a labeled article; and (c) monoaxially heat shrinking the labeledarticle at a temperature of about 100° C. to circumferentially envelopthe at least two portions of the outer surface to closely andsubstantially uniformly follow the portions' contour.
 13. The method ofclaim 12, wherein the heat shrinking is carried out by steam.
 14. Themethod of claim 12, wherein the polymeric sheet is prepared by short-gapstretching.
 15. The method of claim 12, wherein the polymeric sheetcomprises at least two materials, wherein at least one of the at leasttwo materials has a density greater than 1 g/cm³.
 16. The method ofclaim 15, wherein the polymeric sheet comprises up to 50 wt. % of cyclicolefinic copolymer and/or cyclic olefinic polymer (COC/COP).
 17. Themethod of claim 15, wherein the at least one material is polystyrene(PS) or PETg (Poly(ethylene terephthalate) glycol).
 18. The method ofclaim 15, wherein the materials are in the form of layers.